Thickened lubricant containing a carbinoxyaminosilane



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THICKENED LUBRICANT CONTAINING A CARBINOXYAIVIINOSILANE Ernest C. Milberger, Maple Heights, Ohio, assignor to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Filed Jan. 19, 1953, Ser. No. 332,081

3 Claims. (Cl. 252-48) This invention relates to a water resistant thickened lubricant in which an inorganic substance is the thickening agent.

The flow properties of mineral lubricating oils do not always permit their use where a lubricant is required which must adhere to the parts to be lubricated, such as in wheel bearings. For this reason many materials have been added thereto to thicken them. Soap has been widely used for this purpose and soap-thickened mineral lubricating oils generally are known as greases.

There are two general types of greases, those made with a calcium base soap and those made with a sodium base soap. Soda base greases have relatively satisfactory temperature susceptibility characteristics but they deteriorate readily in the presence of water. Greases made with a calcium soap have better resistance to water but lose their consistency or thin out at elevated temperatures. These common soap base greases therefore are not entirely satisfactory with respect to both high temperature susceptibility and water resistance.

Greases prepared using aerogels of a material not soluble in oil, such as silica aerogels, have been proposed. These have excellent high temperature susceptibility properties and in fact are superior in this respect to the soap base greases but, unfortunately, are even more susceptible to deterioration in the presence of water than soap base greases. It is thought that this deficiency is due to a preferential Wetting of the aerogel by water so that in the presence of water the oil phase leaves the aerogel and the thickened character of the lubricant is lost.

In accordance with this invention, lubricating oils thick ened with a nonabrasive inorganic thickening agent such as a finely divided silica aerogel are combined with an oil dispersible water insoluble carbinoxyaminosilane having the general formula:

where n is an integer from 1 to 3 and R is a carbinoxy radical, i.e. an alkyl, alicyclic, aralkyl, alkaryl or aryl group, preferably having less than 8 carbon atoms, such as straight and branched chain methyl, ethyl, butyl, amyl, hexyl and octyl groups, phenyl, benzyl, tolyl, cyclohexyl and cyc'lopentyl groups. The R radicals can be the same or diiferent in compounds where n is 2 or 3. At least one of the RO groups should be resistant to hydrolysis by water; tertiary alkoxy groups are most resistant, and primary alkoxy groups least resistant, with secondary alkoxy, phenoxy and cycloalkoxy groups intermediate these in resistance to hydrolysis.

Exemplifying carbinoxyaminosilanes which can be employed are di-tert-butoxydiaminosilane, di-tert-butoxy-nbutoxyaminosilane, tert-butoxyethoxydiaminosilane, tertbutoxytriaminosilane, tert amoxydimethoxyamin osilane, phenoxytriaminosilane, phenoxyethoxydiaminosilane, di tert-amoxydiaminosilane, di-sec-butoxydiaminosilane, diisopropoxydiaminosilane, di-isobutoxydiaminosilane, diisobutoxy-tert-butoxyaminosilane, tri-tert butoxyamino- States Patent C) silane, triethoxyaminosilane, dimethoxy-tert-butoxyaminosilane, and bis-l-ethylcyclohexoxydiaminosilane.

ties and is highly resistant to deterioration in the presence.

of water.

The preparation of the thickened lubricant is simple and readily adaptable to continuous operation as contrasted with the involved grease-making techniques which are often considered in the industry as an art. The oil stock used in making the thickened lubricant can be widely varied as contrasted with present grease-making requirements in which the oil in many cases is critical to meet certain specifications.

In addition, the avoidance of the use of soap permits the manufacturer to be independent of the supply, which is important in periods in which fats and soaps are scarce and many times of pronounced non-uniformity.

The inorganic gelling agent to be used in making the thickened lubricant in accordance with this invention can be any inorganic material which forms a gel with a lubricating oil and which is so finely divided as to be nonabrasive. The preferred materials are the aerogels which may be formed from any material not incompatible with oil, such as silica, alumina, and other gel-forming metal oxides.

A series of silica aerogels which can be used as the inorganic gelling agent of the invention are manufactured by Monsanto and marketed under the trade name Santo-' cel.

Santocel C is prepared from a sodium silicate solution in the following way: The solution is neutralized with sulfuric acid and then allowed to stand until the mixture sets to form a hydrogel. The by-product sodium sulfate is washed out by the repeated washings with water. The continuous water phase in this hydrogel is then replaced by continued washing with alcohol until an alcogel is formed. In order to remove the liquid phase without a collapse of the gel structure, the alcogel is placed in an autoclave which is then heated above the critical temperature of the alcohol and the pressure is allowed to increase to a point above the critical pressure of the alcohol. The vent valve is then opened and the alcohol allowed to escape. Under these conditions, the silica gel structure remains practically undisturbed and the liquid phase of the gel is replaced with air. The material is then reduced in particle size by blowing it through a series of pipes containing sharp bends with jets of compressed air. Santocel C has a secondary agglomerate particle size of about 3 to 5 microns.

Santocel A is prepared as set forth for Santocel C up to the point of removal of the product from the autoclave. This material is run through a continuous heat ing chamber where'it is heated for /2 hours to a'temperature of about 1500 F. to eliminate the last traces of volatile material. It is then broken down in a reductionizer or micronizcr to a particle size of about inch indiameter. The solids content of the original hydro gel used in preparing Santocel C is approximately 25% higher than that of Santocel A. a

AR is a modification of A, diifering only in that the material is reductionized to about the same particle size as C, approximately 1 to 6 microns in diameter.

ARD is a modification of AR, differing only in that ARD is densified by extracting air under vacuum, an therefore has a smaller volume than AR.-

AX is an A which has not been devolatilized.

CDv is a C which has been devolatilized asset fort for Santocel A. The Santocel is reductionized before being devolatilized.

CDvR differs slightly from CDv in that the CDvR has been devolatilized just after heating in the autocalve and Patented Nov. 22, 1960" I Density, grams/ ml.

AR 0.029 ARD 0.05 to 0.064 c 0.082

In general, AR and ARD show superior gelling ability and the As in general are better than the GS. Silica aerogels which have been devol'atilized generally have a higher gelling efliciency than the undevolatilized aerogels.

In preparing thickened lubricants it is necessary to remove the water from the sol and replace it with an oil. This is. possible by formulating the lubricant and removing the water by flash distillation or azeotropic distillation.

Other types of inorganic gelling agents which may be used include a fumed silica marketed by B. F. Goodrich Company. It is finely divided and appears very much like an aerogel. It is made by a combustion or vaporization process, as. a source of white carbon black for the rubber industry. The particles are several microns in size and porous in nature.

Another material is Linde Silica Flour marketed by Linde Air Products Co. It is very similar in physical appearance to the silica aerogel. The particle size of the silica is purported to be 0.01 to 0.05 micron and to be manufactured by burning silicon tetrachloride and collecting the combustion product on cool plates analogous to the production of carbon black. The particles are thought to be aggregates or clusters of particles rather than of sponge-like character.

Still another inorganic gelling agent known is Ludox silica from DuPont, which is known as a silica sol, and silica derivatives thereof. It has a particle size of the order of 0.01 to 0.03 micron.

No attempt is made to enumerate all of the inorganic gelling agents which will be suitable, nort to present examples of all of them since the novel aspects of the invention reside in water-proofing the lubricant rather than the use of novel gelling agents, per se.

The lubricating oil to he used in the process may have any lubricating viscosity. It may be raw oil, acid refined, or solvent refined, as required for the particular lubricating need.

The nature of the base oil has been found to make little difference in the relative consistencies of the thickened lubricants and conventionally (acid) refined oils produces slightly thicker lubricants than solvent refined oils. Excellent working stability is obtained regardless of the type of the base oil. An increase in the viscosity of the base oil, as might be expected, brings increased viscosity to the thickened lubricant, and minimizes bleeding. The change is relatively small and fairly linear. The viscosity of the oil does not affect the working stability of the lubricant.

The relative proportions of the inorganic gelling agent and the oil will vary somewhat depending upon the desired body in the thickened lubricant, the gelling ability of the inorganic gelling agent and the viscosity of the Oil used. It has been noted, for instance, that with the Linde Silica Flour, the lubricants are somewhat harder, i.e., have a lower penetration than lubricants, containing the, same, weight of Santocel. Lubricants made, with lower viseosity oils require a somewhat larger amount of the inorganic gelling agent to give a lubricant of the same penetration. The thickened lubricant may vary in consistency from the consistency of a slightly thickened oil to a solid or semi-solid of grease-like consistency. In general the amount of the inorganic gelling agent falls within the range of 5 to 20%, and in most cases would fall within the range of 7 to 12%.

The amount of the inorganic gelling agent, as might be expected, affects the consistency of the thickened lubricant in that an increase in its concentration brings a corresponding increase in consistency. The range is fairly linear and the, amount of the gelling agent can be selected with relation to the consistency desired in. view of theinformation in the following examples. While the difierence is slight, the lubricants made with lower concentrations of gelling agent possess better working stability, while lubricants with large amounts of gelling agent show slightly improved temperature susceptibility characteristics. The bleeding tendencies are decreased by increasing concentrations, of the gelling agent.

In general, the properties of the thickened lubricants are remarkably independent of the composition variables and are not critical. The relative concentration of the gelling agent effects the most significant alteration, particularly with regard tofthe final consistency of the prod not. This permits the manufacture of thickened lubricants having a widevariety of consistencies.

A wide variety of oil-dispersible Water-insoluble carbinoxyaminosilanes can be employed in accordance with the invention to improve water resistance of oil base aerogel greases.

The carbinoxyaminosilane need not be oil-soluble but it should be oil-dispersible.

The carbinoxyaminosilane is incorporated in the aerogel base grease in a concentration ranging from about 0.2 to about 2% by weight and this concentration gives satisfactory results. There is no reason to employ more carbinoxyaminosilane than is necessary to achieve the desired effect, but excessive amounts do no harm and amounts up to 5% or higher have been employed.

The composition is made simply by mixing the inorganic gelling agent, the oil and the carbinoxyaminosilane in any order or manner. In one embodiment the carbinoxyaminosilane can be incorporated with the inorganic gelling agent either by mixing directly or with the aid of a solvent, adding the oil, mixing the solution with. the inorganic gelling agent and then evaporating the solvent. Generally the carbinoxyaminosilane is dispersed in the oil and the inorganic gelling agent added thereto and mixed therewith. Any simple mixing technique can be employed and, ifdesired, the mixture can be homogenized in a colloid mill although this is not necessary.

The composition of the invention isnot limited to the oil, gelling agent and carbinoxyaminosilane. Any of the materials conventionally added to lubricants and greases can be included. The expresssion consisting essentially of as. used herein is, intended to. refer to the components which are essential to the composition, namely, the oil, the inorganic gelling agent and the carbinoxyaminosilane, and the expression does not exclude other components from the composition which do not render it unsuitable for lubrication, such materials being, for instance, high polymers to modify viscosity or viscosity index, materials to impart tackiness, lubricating solids such as graphite, antioxidant additives, corrosion inhibitors of various types, sulfur, additives to render the lubricant suitable for use in gears, for cutting, grinding, etc.

The following example illustrates the invention:

Example A grease was compounded of 89 weight percent base oil, 10 weight percent Santocel C and 1 weight percent of Sylon RD 602 (di-tert-butoxydiaminosilane) having a boiling pointof 171 C. (-760 mm), a refractive index of 1.4 245 (20 C.) and a specific gravity of 0.926. The

base oil used was a No. 300 Red Oil (an acid-refined oil having a viscosity of 300 SSU at 100 F The alkoxyaminosilane was dissolved in the weighed portion of base oil and thoroughly mixed with a Lightnin stirrer. The Santocel C was added to this mixture and stirred, after which the composition was thoroughly mixed for 20 minutes in a greasemaker at 57 revolutions per minute. The grease then was allowed to age undisturbed for 17 hours.

The water resistance of the grease was determined by the plate test as follows: A 2 x 2 inch stainless steel plate was coated with a uniform layer of the thickened lubricant and then immersed in a 150 cc. beaker filled with water at room temperature. The coated Plate was allowed to stand undisturbed overnight, after which the coating was rated according to a strictly empirical visual observation. If the lubricant had been broken down completely the rating was 0, and if the lubricant showed no change the rating was 10. In this test the lubricant had a water plate rating of 10. The lubricant without Sylon RD 602 had a rating of 0.

A second sample of the lubricant was tested by the boiling water plate test. This test is more severe than the plate test. A ,6 inch thick circular coating of grease 1V2 inches in diameter was placed ona 2 x 2 inch stainless steel plate. The plate was immersed in Water and the water heated to the boiling point and kept at that temperature until the coating decomposed. This required 29 minutes. For comparison, a conventional calcium soap base wheel bearing grease decomposed in 18 minutes, showing that the carbinoxyaminosilane grease had superior water resistance. Inasmuch as a conventional wheel bearing grease is a generally accepted grease in commerce, this test denronstates the superior use properties of the thickened lubricant of the invention.

It is thought that the carbinoxyaminosilane is effective to improve the water resistance of the aerogel base grease because it attaches itself to the silica aerogel and protects it from the water so that it is not wet by the water and therefore does not separate from the oil in the presence of water. The effect may possibly be due to the cationic character of the amino group attached to the carbinoxyaminosilane molecule. From this it would follow that the more amino groups the carbinoxyamiuosilane possesses,

the more eifective it would be expected to be in improvl5 2,584,085

ing the water-resistance of the grease. In actual practice it has been found that although the carbinoxyaminosilanes may vary to a certain extent in elfectiveness, any lessening in water-resistance imparted to the lubricant can be adjusted by increasing the amount employed of the carbinoxyaminosilane.

Any efl'ect of the carbinoxyaminosilane in lowering the consistency of the thickening lubricant can be overcome by employing a larger percentage of thickening agent and therefore it not a disadvantage.

The thickened lubricants of the invention possess a markedly superior water-resistance and excellent temperature susceptibility properties. The carbinoxyaminosilaue and silica aerogel in contrast with soap are not subject to oxidation or like deterioration in storage. In fact in some instances an improvement in water-resistance has been noted after the grease has been permitted to age for from 12 hours to several weeks. By varying the proportions of thickening agent and oil stock and the character of the oil stock, the properties of the thickened lubricant of the invention can be widely varied in order to meet the requirements of almost any lubricant specification.

I claim:

1. A water-resistant thickened lubricant of good high temperature susceptibility properties consisting essentially of a mineral lubricating oil of lubricating viscosity as the major component, a silica aerogel in an amount suflicient to impart a greaselike consistency to the oil upon addition thereto as a minor component and a carbinox-yaminosilane in an amount less than the gelling agent sufficient to impart stability to the lubricant against deterioration by water.

2. A water-resistant thickened lubricant in accordance with claim 1 in which the carbinoxyaminosilane is an alkoxyaminosilane.

3. A water-resistant thickened lubricant in accordance with claim 2 in which the alkoxyaminosilane is a dialkcxydiaminosilane.

References Cited in the file of this patent UNITED STATES PATENTS 2,583,604 Sirianni et al. Jan. 29, 1952 2,583,606 Sirianni et al Ian. 29, 1952 Stross Jan. 29, 1952 

1. A WATER-RESISTANT THICKENED LUBRICANT OF GOOD HIGH TEMPERATURE SUSCEPTIBILITY PROPERTIES CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL OF LUBRICATING VISCOSITY AS THE MAJOR COMPONENT, A SILICA AEROGEL IN AN AMOUNT SUFFICIENT TO IMPART A GREASELIKE CONSISTENCY TO THE OIL UPON ADDITION THERETO AS A MINOR COMPONENT AND A CARBINOXYAMINOSILANE IN AN AMOUNT LESS THAN THE GELLING AGENT SUFFICIENT TO IMPART STABILITY TO THE LUBRICANT AGAINST DETERIORATION BY WATER. 